Tag Archives: ACOG

Optic of the week: Trijicon TA01NSN ACOG

The TA01NSN ACOG is a classic at this point.  A compact fixed 4x scope with a bullet drop chart calibrated for M855 out of a carbine barrel.  People assume it is calibrated for a 14.5 inch M4 barrel, but every time Trijicon has given numbers it sounds like the Bullet Drop Chart (BDC) was based around a 16 inch barrel.

The main thing that sets the TA01NSN ACOG apart from the majority of the other models of ACOGs are the iron sights mounted on it.

The iron sights on this ACOG are more for emergency use, for example should you manage to break the ACOG, or for use in heavy rain at close distances, etc.

The front sight is adjustable for windage, the rear sight is not adjustable.  This front sight also has a vial of Tritium in it allowing it to be seen at night.  In the past, there have been people who expressed a concern about this revealing their location.  If this is a concern to you, the sight can be removed, or simply taped over.

I’ve found some of the TA01NSN ACOG iron sights to shoot massively off left or right, so you will want to check it out before you rely on them.

Older ACOGs have 1/3 MOA adjustment that requires a tool like a coin to adjust.  Newer ACOGs have a 1/2 MOA capped turret that is tool less.

The adjustment caps on the TA01NSN are not tethered.  On some other models they are.  When I was zeroing this old ACOG, the O-ring used to seal the elevation knob broke apart.  I notice this O-ring is amber, while ever other O-ring on the ACOGs I own (and on the windage) are orange leading me to believe that this was a replacement done by the previous owner.  You can see the failed amber colored O-ring in the picture above.

I have seen the adjustment cap threads cross threaded or stripped from abuse.  While ACOG scopes are tough, nothing is impervious to user error. & abuse.

ACOG adjustments can be very annoying.  First, don’t try to turn the adjustments to the extremes, that can damage the scope.  Second is that the scope adjustments can hang.  The scope is compact due to a prism and the adjustments rely on the prism moving against a spring.  This means that sometimes when you dial in an adjustment the scope prism won’t actually mode until you smack the scope or fire a couple of shots.  Normally this would be considered very unacceptable in a scope, but in this case it is considered a quirk of the compact tough ACOG.

The center of the TA01NSN crosshair is meant to be zeroed for 100 meters.  Then each hash mark represent a 19 inch width (a mans shoulder width) at the distances of 200 to 500 meters.  The very top of the bottom thicker bar is the 600m mark.

The 4x magnification aids in locating and identifying targets.  When used on a rifle with a fixed front sight base the shadow of the base will appear in the field of view.  Personally I don’t think it seems as bad as it shows in the picture, but I know it really irritates some people.

I took this opportunity to try the Elcan Specter DR in 4x mode and the TA01NSN side by side.  For speed of acquiring a target, or moving from target to target I felt they were the same.  I would say the increased eye relief of the Elcan may make it a far better choice for a .308 or other higher recoiling rifle.  But for shooting 4x on a 5.56 I didn’t feel one offered any significant advantage over the other.

A last point, the ACOG scopes have tritium illumination.  There are some newer models that use batteries.  The idea behind the tritium is to provide battery free illumination of the reticle in low light situations.  I’ve found that often when it is dark enough to use the illumination, I can’t see the target.  Since the half life of Tritium is about 12 years, some of the older ACOGs got gotten very dim.  Trijicon will relamp a scope for a price, but it will likely be more cost effective to sell an old ACOG and just buy a new one.

I really love the old TA01NSN, but now variable 1-X scopes are taking over that nitch.  While the newer 1-X power scopes tend to be larger, heavier, and far less durable than the venerable ACOG, the capability they offer are leading more people to choose that over the ACOG.  If you are primarily expecting to identify and engage man sized targets at 100-600 meters the ACOG is hard to beat.  If you need the fastest speed for up close, or precision sub-MOA shooting, look elsewhere.

ACOG EREK

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I managed to purchase for my self an ACOG EREK cantilever adapter.

Now to be honest, I’m not exactly sure what EREK stands for.  I’m guessing something like Eye Relief Extension Kit.

So why did I buy it?  Because I wanted one.  Some time back, I saw some pictures of the USMC trying a cantilever mount for the ACOG on the M16A4.  Since them I have wanted to give it a try.

When you read about people complaining about the ACOG, the first complaint is always price, the second tends to be about the short unforgiving eye relief.  Once you take that short eye relief of the ACOG and have to mount a BUIS behind it, combined with a fixed stock, it can be annoying.  Personally, not only have I gotten used to it, I am rather fond of the ACOG mounted forward as I shoot nose to the charging handle.

So at some point the USMC had some adapters made up that moved the ACOG back and over the Knights 2-600m rear sight.  This makes the ACOG easier to use with the A2 fixed stock.  Now I tried to find pictures of it in use again, but I was unable too.  My guess is that the USMC tested it and for what ever reason decided not to use them.

Why?  I don’t know.  Perhaps raising the ACOG up make it more unacceptable to damage or abuse changing the zero.  It might not have been worth the cost.  Or someone might have come to their senses and said use the M4 instead.  In any event, I have one to use now, and it is rather nice.  It lifts the ACOG up enough that the charging handle is easily accessible, and moves the ACOG far enough back that you don’t need to crane your head forward for nose to the charging handle.

 

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Testing the 5.56mm MK318 MOD 0 / 5.56 SOST ammo

The 5.56 SOST  is the ammo currently being used by the USMC and other troops in the GWOT,  it has not been available for the public to buy for very long so I, like a lot of other people have been curious about how it performs. The round was designed to  have better terminal performance and accuracy from short barreled rifles with a muzzle velocity of 2925 fps from the 14.5 inch M4 barrel.  The round is a OTM,  this is important to remember as it is not the same as a hollow point.  It does however, offer up better performance and is barrier blind. The bullet itself has a thick copper base and a lead front end with the usual open tip that results from the process of making the bullet.  Also present are the rings seen around the bullet much like a barnes triple shock X.  A lot of people assumed and still do that the SOST is a barnes solid copper TSX, but it is not.

After getting my hands on some of the ammo I decided to test it for accuracy first. Since the ammo is intended for combat weapons, I chose to use my Colt 6940  with milspec barrel with 1/7 twist. I did put a Leupold 18x target scope on the carbine though so i could get all the accuracy out of it I could.  I fired 2 strings of 5 shots at 1 inch dots and one string of 10 shots of M855 to compare it to the common military load all at 100 yards. It was around 1100 AM , sunny with a  2 oclock 18 MPH wind.

Other then the normal 1st round flyer you usually get from hand cycling the action as opposed to letting the recoil operate and chamber  the next few rounds, the ammo showed some  great potential. The group on the left  was a little worse due to my own bad trigger work and lost concentration on one shot, but still pretty good considering. Now I know some claim  5 shot groups tell nothing, but if you over lay to  strings you get a pretty good idea  and you keep barrel heat down and mirage off the barrel messing with the scope.

After shooting the groups I decided to test out how the round matched the trajectory of the M855 since that is one of the things the SOST round was meant to have in common with the green tip. Out to 300and 400 yards  the SOST did match the BDC of my TA31F  ACOG and zero of other scopes and Aimpoint RDS I had on hand zeroed for the green tip. Also when comparing the position of the groups in relation to the aiming points, you can see on paper that the zero held very close for both rounds.

Now, the real surprise for me, was how good the lot of M855 I shot turned out to be!  Many gun board expurts and gun magazine expurtitions will gladly tell you how terrible green tip is in the accuracy department along with its many other flaws , makes it  slightly more useful then tits on a boar hog. After getting the carbine hot  after some drills using the SOST and playing around, I fired off 10 rounds fairly quickly  with the Colt/18x combo.  The results left me a little surprised, rarely have I seen green tip shot for accuracy  with sand bags, a table and a target scope further then 50 yards. And I do not recall having seen any pictures of it doing as well in a true 100 distance group.  I shot the green tip with all seriousness and the same concentrated effort I did with the SOST and the results were pleasing and a little surprising to me.  I have never taken the green tip seriously  enough for my own needs in the accuracy department so this will indeed lead to more testing of the M855 if for no other reason  then to see if this was a fluke.

Now I do not mean to sound like I think green tip is crap, I have seen some  good performance out of it at longer ranges on coyote size targets and even man sized targets. But on the other hand, I have seen some terrible accuracy from it too. Of course lots and different MGGs have as much to do with it as anything, not to metion the different shoots and the quality or lack of  in the guns used.

Back to the SOST, I think its a pretty good round from what I can tell. It is not MK 262 or TAP 75 gr. But for general issue to everyone, it is an iprovement in my humble opinion.  I have not shot anything living with it yet, but I will. Also, in the next few weeks I will test it though a few “barriers” like auto glass, wood, and wall paneling. Hopefully I will get to shoot through some auto doors as well.  I would not use it in my own house if over shooting is a issue, but I would use it for anything else at this point if you can find enough for SHTF bulk storing. And you have the benefit of practicing/training with M855 and still being able to shoot the SOST without a zero change. At this point I can not say it is better then any MK 262 top load in accuracy, but it is not meant to be, but, it is better then M193 by a long ways and it shows the ability to shoot a lot better the M855 and even if it just matches it in accuracy you still have the benefits of better terminal performance and barrier penetration while still holding together to hit the target behind if power point presentations can be believed. Hopefully my future testing will offer at least a tiny sample to help prove or disprove the new round.

Ranges Notes

Had a Colt 6920 with a Trijicon TA31-MRD ACOG and a Spikes 5.45 with a TA31-ECOS ACOG side by side at the range today.  Both were zeroed using the 300m point of aim at 25 meters.  Later that day, both were used to shoot at a steel target at 565 yards(about 500 meters).  The Colt using M855 ammo and the ACOG calibrated for that ammo was right on for elevation when using the 500m mark.  However when shooting at 500m with the 5.45 and an identical 5.56 Bullet Drop Chart reticle, the 5.45 corresponded to the 400 meter mark on the BDC.

It was interesting to see how much flatter the 5.45 was flying compared to the same zero at the M4.  I’ve never been able to find good data on the ballistic coefficient of the 5.45 7n6 rounds, or readable info on its trajectory.